Pawl and ratchet clutch with shifting pawl

摘要

A pneumatic starter (10) incorporates a pawl and ratchet clutch assembly (50) having a ratchet member (46) mounted to a drive member (40) powered by an air expansion turbine (20), and a plurality of pawls (48) disposed circumferentially about the ratchet member (46) and operable in engagement therewith to transmit rotational drive torque from the drive member (40) to a driven member (60). Each of the pawls (48) is supported on a pivot pin (54) for pivotal movement into and out of engagement with the ratchet member (46) and translation between a engaged and drive position and a disengaged and retracted position to effectuate a change in the location of the center of gravity (93) of the pawl relative to its pivot axis (55). Preload springs (54) are provided for biasing the pawls (48) to pivot radially inwardly into engagement with the ratchet member (46). A torsion spring (82) is disposed in operative association with each pawl (48) for shifting its associated pawl from its engaged and drive position to its disengaged and retracted position upon lift-off of the pawl from the ratchet member.